334 research outputs found
A New Analytical Procedure for Solving the Non-Linear Differential Equation Arising in the Stretching Sheet Problem
The paper discusses a new analytical procedure for solving the non-linear boundary layer equation arising in a linear stretching sheet problem involving a Newtonian/non-Newtonian liquid. On using a technique akin to perturbation the problem gives rise to a system of non-linear governing differential equations that are solved exactly. An analytical expression is obtained for the stream function and velocity as a function of the stretching parameters. The Clairaut equation is obtained on consideration of consistency and its solution is shown to be that of the stretching sheet boundary layer equation. The present study throws light on the analytical solution of a class of boundary layer equations arising in the stretching sheet proble
Ultra-high-resolution observations of CH in southern molecular cloud envelopes
We present a miniâsurvey of ultrahighâresolution spectroscopy (UHRS) of CH towards three southern molecular cloud envelopes. The sightlines are selected to probe physically similar gas in different Galactic environments. With a velocity resolution of âŒ0.5âkmâsâ1(R=575â000) these observations resolve most kinematic components of the absorption lines. We do, however, detect one line component in the Lupus region, which is not resolved and for which an upper limit of b<0.3âkmâsâ1 is found. We find a correlation between distance of the absorbing gas from the Galactic midâplane and the fractional abundance of CH. We show that this correlation can be explained as being a result of a fallâoff in the ultraviolet radiation field intensity and propose that CH observations in carefully selected sightlines might allow a mapping of the variations in the interstellar radiation field
J/Psi Suppression in Heavy Ion Collisions at the CERN SPS
We reexamine the production of J/Psi and other charmonium states for a
variety of target-projectile choices at the SPS. For this study we use a newly
constructed cascade code LUCIFER II, which yields acceptable descriptions of
both hard and soft processes, specifically Drell-Yan and hidden charm
production, and soft energy loss and meson production, at the SPS. Glauber
calculations of other authors are redone, and compared directly to the cascade
results. The modeling of the charmonium states differs from that of earlier
workers in its unified treatment of the hidden charm meson spectrum, which is
introduced from the outset as a set of coupled states. The result is a
description of the NA38 and NA50 data in terms of a conventional hadronic
picture. The apparently anomalous suppression found in the most massive Pb+Pb
system arises from three sources: destruction in the initial nucleon-nucleon
cascade, use of coupled channels to exploit the larger breakup in the less
bound Chi and Psi' states, and comover interaction in the final low energy
phase.Comment: 36 pages (15 figures
Systematics, taxonomy and floristics of Brazilian Rubiaceae: an overview about the current status and future challenges
Uma nova espécie de Coussarea Aubl. (Rubiaceae) para a mata atlùntica no estado da Bahia, Brasil
Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays
Bose-Einstein correlations of both neutral and like-sign charged pion pairs
are measured in a sample of 2 million hadronic Z decays collected with the L3
detector at LEP. The analysis is performed in the four-momentum difference
range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be
smaller than that of charged pions. This result is in qualitative agreement
with the string fragmentation model
Measurement of beauty production in deep inelastic scattering at HERA
The beauty production cross section for deep inelastic scattering events with
at least one hard jet in the Breit frame together with a muon has been
measured, for photon virtualities Q^2 > 2 GeV^2, with the ZEUS detector at HERA
using integrated luminosity of 72 pb^-1. The total visible cross section is
sigma_b-bbar (ep -> e jet mu X) = 40.9 +- 5.7 (stat.) +6.0 -4.4 (syst.) pb. The
next-to-leading order QCD prediction lies about 2.5 standard deviations below
the data. The differential cross sections are in general consistent with the
NLO QCD predictions; however at low values of Q^2, Bjorken x, and muon
transverse momentum, and high values of jet transverse energy and muon
pseudorapidity, the prediction is about two standard deviations below the data.Comment: 18 pages, 4 figure
Study of Inclusive Strange-Baryon Production and Search for Pentaquarks in Two-Photon Collisions at LEP
Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons
in two-photon collisions with the L3 detector at LEP are presented. The
inclusive differential cross sections for Lambda and Xi- are measured as a
function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The
mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event
is determined in the kinematic range 0.4 GeV < pt< 2.5 GeV, |eta| < 1.2.
Overall agreement with the theoretical models and Monte Carlo predictions is
observed. A search for inclusive production of the pentaquark theta+(1540) in
two-photon collisions through the decay theta+ -> proton K0s is also presented.
No evidence for production of this state is found
Effects of thermal buoyancy and variable thermal conductivity on the MHD flow and heat transfer in a power-law fluid past a vertical stretching sheet in the presence of a non-uniform heat source
Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA
Differential inclusive jet cross sections in neutral current deep inelastic
ep scattering have been measured with the ZEUS detector. Three phase-space
regions have been selected in order to study parton dynamics where the effects
of BFKL evolution might be present. The measurements have been compared to the
predictions of leading-logarithm parton shower Monte Carlo models and
fixed-order perturbative QCD calculations. In the forward region, QCD
calculations at order alpha_s^1 underestimate the data up to an order of
magnitude at low x. An improved description of the data in this region is
obtained by including QCD corrections at order alpha_s^2, which account for the
lowest-order t-channel gluon-exchange diagrams, highlighting the importance of
such terms in parton dynamics at low x.Comment: 25 pages, 4 figure
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